1. Field of the Invention
This invention relates to a hammer-drive powder-actuated tool, and more particularly to a hammer-drive powder-actuated tool that has a high success rate in ignition of a primer and that is safe to use.
2. Description of the Related Art
Referring to FIG. 1, a conventional hammer-drive powder-actuated tool 1 includes a tubular tool body 11, an inner tube 12 movable forwardly and rearwardly within the tool body 11, a sleeve 13 connected to a rear end of the inner tube 12 and formed with an accommodating chamber 131 for receiving a powder cartridge (not shown), a piston 14 movable forwardly and rearwardly within the inner tube 12, and a firing device 15.
The firing device 15 includes a pin holder 151 disposed within the tool body 11 and abutting against a rear end of the sleeve 13, a firing pin 152 extending into the pin holder 151, a coiled compression spring 153 sleeved on the firing pin 152 and abutting against the pin holder 151, a nut 154 engaging an externally threaded rear end of the firing pin 152 and abutting against a rear end 157 of the coiled compression spring 153, and a positioning pin 158 extending through the nut 154 and the externally threaded rear end of the firing pin 152 to fix the nut 154 relative to the firing pin 152. The pin holder 151 has a front end formed with a cavity 156. The firing pin 152 has a head 155 disposed within the cavity 156.
During use, a hammer (not shown) is operated to strike the externally threaded rear end of the firing pin 152 to move the head 155 of the firing pin 152 into contact with the powder cartridge so as to ignite the powder cartridge to thereby drive forward movement of the piston 14.
The abovementioned conventional hammer-drive powder-actuated tool l 1 suffers from the following disadvantages:    (1) The head 155 of the firing pin 152 has a diameter much larger than that of the rear end of the powder cartridge. As such, when the powder cartridge is stricken by the firing pin 152, if the central axis of the firing pin 152 is inclined relative to that of the powder cartridge, misfire may occur.    (2) To prevent accidental removal of the powder cartridge from the chamber 131 when the tool 1 is in an upright state such that the cartridge is disposed above the firing pin 152, a reed spring 159 is disposed on a front end of the pin holder 151 and between the head 155 of the firing pin 152 and the powder cartridge. In case of accidental dropping of the tool 1, however, the powder cartridge may hit the reed spring 159 by virtue of the gravity of the inner tube 12 and the sleeve 13 to result in ignition of a primer of the powder cartridge, thereby affecting safety during use.